Limiting the energy consumption of computers, especially portables, is becoming increasingly important. New energy-saving computer components and architectures have been and continue to be developed in different aspects such as circuit design, battery technology, semiconductor technology, and communication systems. The problem is to minimize energy consumption while not significantly impacting the effective performance of the wireless device.
Fourth-generation systems will likely not use a single standardized air interface, but a set of different technologies and standards. Additionally, the fixed network system will also be a part of future heterogeneous network systems. Therefore, an intensive effort to reduce power consumption is required.
Handheld portable devices are composed of a combination of digital, mixed signal, and even radio frequency circuits that together perform all of the functionality required to communicate across the heterogeneous wireless environment. The need to communicate with people using different types of equipment can only be solved with software reprogrammable radios. A software programmable radio can communicate with many different radios with only a change in software parameters.
A typical handheld portable device has an acceptable weight range between 4-12 oz. for most handheld applications based on human factor studies. The well-known nickel cadmium (NiCd) batteries, lithium-ion (Li-ion) batteries, and nickel metal hydride (NiMH) batteries are popular; however, multiple access systems need more powerful batteries and other technologies to reduce battery drain. Unfortunately, significant improvements in battery technology are not expected in the next few years because battery technology typically only doubles in performance in energy density roughly every 35 years.
One way to reduce energy consumption is to use and develop components that consume less power. Another way is to use components that can enter low power modes by temporarily reducing their speed or functionality. For this scheme, one strategy is to compress TCP/IP headers, which reduces their size by an order of magnitude, thereby reducing the wireless communication activity of a mobile client. Another way is to reduce the data transmission rate or stop data transmission altogether when the channel is bad, i.e., when the probability of dropped packets is high, so that less transmission time is wasted sending packets that will be dropped.
Another method is to use a medium access control protocol that dictates in advance when each wireless device may receive data. In addition, another strategy is to have servers or proxies use information about mobile client characteristics and data semantics to provide mobile clients with versions of data with reduced fidelity and smaller size, which reduces the amount of energy mobile clients must expend to receive the data. For example, a data server might convert a color picture to a black-and-white version before sending it to a mobile client. Of course, it is necessary to design applications that avoid unnecessary communication, especially in the expensive transmit direction.
Another need exists for systems that are capable of determining paging areas in heterogeneous access networks. Other areas of interest in heterogeneous access networks include authentication, association and methods for activating access network interfaces in heterogeneous access networks.